Table 1.
Physical-chemical characteristics of the collected soil samples used for the isolation of rock phosphates-solubilizing bacteria.
Data are given as means ± standard deviation (n = 3).
Table 2.
Soluble-P content and RP-solubilization ability (RP solub.) of bacterial strains in NBRIP liquid media with NH4+ or NO3- as the sole N source after 7 days of culture.
Data are given as means ± standard error (n = 3). The same lowercase letters in each column indicate a lack of significance (p<0.05) among the different bacterial strains.
Fig 1.
Bacterial growth, soluble-P content (μg Pi mL-1) and pH of each isolate cultivated in NBRIP with rock phosphate (RP) and NH4+ as the sole source of N after 0, 3, 7, 14, and 21 days of culture.
Values represent the means and the standard error (n = 3). The effect of bacterial strains (Bs), time of incubation (T) and their interactions (Bs*T) were analyzed with a two-way repeated ANOVA for each variable measured (OD 600nm, soluble-P content and pH). The asterisks indicate the strains with the highest bacterial growth (OD 600nm) over the time of culture. The lower and uppercase letters denote statistical differences in relation to soluble-P content and pH values, respectively, among the isolates after 21 days of experiment.
Fig 2.
Bacterial growth, soluble-P content (μg Pi mL-1) and pH of each isolate cultivated in NBRIP with rock phosphate (RP) and NO3- as the sole source of N after 0, 3, 7, 14, and 21 days of culture.
Values represent the means and the standard error (n = 3). The effect of bacterial strains (Bs), time of incubation (T) and their interactions (Bs*T) were analyzed with a two-way repeated ANOVA for each variable measured (OD 600nm, solble-P content and pH). The asterisks indicate the strains with the highest bacterial growth (OD 600nm) over the time of culture. The lower and uppercase letters denote statistical differences in relation to soluble-P content and pH values, respectively, among the isolates at any time of the experiment.
Table 3.
Concentrations of organic acids (mM) produced by different bacterial strains grown in NBRIP liquid media with rock phosphate (RP) and NH4+ as the sole source of P and N.
Data are given as means ± standard error (n = 3). The same lowercase letters in each row indicate a lack of significance (p<0.05) among the different bacterial strains within each organic acids after 21 days of culture.
Table 4.
Concentrations of organic acids (mM) produced by different bacterial strains grown in NBRIP liquid media with rock phosphate (RP) and NO3- as the sole source of P and N.
Data are given as means ± standard error (n = 3). The same lowercase letters in each row indicate a lack of significance (p<0.05) among the different bacterial strains within each organic acids after 21 days of culture.
Fig 3.
Phylogenetic tree based on 16S rDNA sequence of the 15 bacterial isolates with closely related species of the genus Bacillus, Paenibacillus, Sinorhizobium and Pseudomonas using SH-like test with maximum likelihood method.
Numbers at nodes indicate percentages of occurrence in 100 bootstrapped trees. The scale bar indicates substitutions per nucleotide position.
Table 5.
Identification of the bacterial strains isolated from the soil A, B and C by 16S rRNA sequencing.
Fig 4.
(a) the physical-chemical soil properties in the three sampled sites (A, B and C); (b) the different bacterial strains isolated from the three soils (circles, squares and diamonds indicate strains from soil A, B or C, respectively) with NH4+ (red color) or NO3- (green color) as the sole source of N in relation to the soluble-P content released in the NBRIP liquid media, the production of organic acid (gluconic acid, lactic acid, glycolic acid, acetate, butyrate, formic acid, propionate, pyruvic acid, malic acid, maleic acid, oxalic acid and citric acid) at 21 days of culture and the physical-chemical properties of soil A (Olsen P, NH4+ content and coarse silt), soil B (CaCO3 content and NO3- content) and soil C (coarse and fine sand fraction).